1. Field of the Invention
The invention is based on a clutch system and on a method for controlling a clutch system.
2. Description of the Prior Art
One such clutch system is known for instance from Bosch Kraftfahrtechnisches Taschenbuch [Automotive Handbook], Vieweg (Braunschweig and Wiesbaden), 1999, pages 590f. The automated clutch system shown there for instance has a clutch with a hydraulic actuation unit for connecting and disconnecting a force transmission path between a clutch input side and a clutch output side; a hydraulic connection between the actuation unit and an electrohydraulic actuator; and a control unit for triggering the actuator. In these systems, the distance at the actuation unit of the clutch or at the disengaging gear must be known, to enable controlling the frictional moment at the clutch as precisely as possible. For triggering the hydraulic actuation unit of the clutch in such systems, an electrohydraulic actuator is used. The known devices in some cases have sensors for detecting the adjusting distance of an adjustable clutch part of the actuation unit, and the sensors are integrated with the clutch in a complicated way.
For reasons of cost and space, however, there are also applications that have no sensors at the actuation unit. In that case, the adjustment of the adjustable clutch part is detected indirectly by means of the electrohydraulic actuator. For that purpose, the actuator has an actuator final control element that is adjustable by a predeterminable regulating distance and also has an absolute or incremental distance pickup on the actuator, whose zero position is defined for instance by a mechanical stop of the actuator final control element. It is a prerequisite of such systems that the hydraulic fluid in the hydraulic connection and the hydraulic components connected to of the actuator and of the actuation unit not be compressible and that no leakage occur. Under these ideal preconditions, it is assumed that the distance that the actuator final control element covers is directly proportional to the distance that the clutch part, which is adjustable for connecting and disconnecting a force transmission path between the clutch input side and the clutch output side, covers. The ratio between the regulating distance of the actuator final control element and the adjusting distance of the clutch part is called the hydraulic boost.